Title Physics.pdf ✅

Unit 3 Q.No. Solid Electronic Materials Marks 21 Explain the formation of energy band in solids, on this basis explain the distinction between metals, insulators and conductors along with a neat diagram. 8 22 (a) What are direct and indirect energy bands in solids? (b) Explain the terms: carrier mobility and drift velocity 4 4 23 Write and explain Fermi – Dirac function. How does it vary with temperature? 8 24 Explain the quantum theory of free electrons in metals. Derive an expression for density of energy states in it. 8 25 What is the effect of periodic potential on the energy of electrons in metal? Explain it on the basis of the Kronig – Penny model and explain the formation of energy band. 8 26 (a) A rectangular block of a solid is connected to a dc voltage source. Obtain the expressions for (i) the current density flowing through the block and (ii) the conductivity of the material in terms of concentration of carriers in it. (b) In a solid consider the energy level lying 0.01 eV below Fermi level. What is the probability of this level not being occupied by an electron? 4 4 27 (a) The energy of a photon of sodium light (λ= 589 nm) equals the band gap of a semiconductor material. What will be the minimum energy E required to create hole electron pair? (b) Fermi energy of a given substance is 7.9 eV. What is the average energy and speed of electrons in this substance at 0 K. 4 4 28 (a) In a solid, consider the energy level lying 0.02 eV below the fermi level, calculate the probability of this not being occupied by electrons at room temperature (300 K). Given k = 1.38 X 10-23 J/K. (b) Define: fermi energy, conduction band, valence band, density of states. 4 4 29 (a) For sodium electron concentration is 2.65 X 1022 cm-3 . Find the value of fermi energy. (b) The fermi level for potassium is 2.1 eV. Calculate the velocity of the electrons at the fermi level. 4 4
30 Discuss the Kronig-Penney model for the motion of an electron in a periodic potential and hence explain E-K curve in solids. 8 Unit 4 Q.No. Quantum Mechanics Marks 31 (a)What is a matter wave .Derive the expression for it and discuss the significance of change in mass and velocity on it. (b) Describe Davisson and Germer Experiment. What does it confirm? 4 4 32 Derive time independent Schrodinger wave equation. 8 33 Derive time dependent Schrodinger wave equation. 8 34 State and prove Heisenberg’s uncertainty principle. Explain its consequence with examples. 8 35 Derive one dimensional Shrodinger wave equation for a particle in a box and hence find energy eigenvalue for it. 8 36 (a) Explain the consequences of Heisenberg’s uncertainty principle with an example. (b) Calculate the uncertainty in measurement of momentum of an electron if the uncertainty in its location is 1Å. 4 4 37 (a) What is a wave packet? explain Born interpretation. (b) Calculate the energy required for an electron to jump from ground state to the second excited state in a potential well of width L. 4 4 38 (a) Explain with the help of uncertainty principle why electron cannot reside inside the nucleus. (b) Write the properties of wave function . 4 4 39 Derive expression for energy eigen value and normalized eigen function for a particle trapped in one dimensional infinite potential well of width a. 8 40 (a) Uncertainty in time of an excited atom is about 10-8 sec. what are the uncertainty in energy and in the frequency of radiation. (b) Explain the expectation values of the dynamical variables. 4 4